A new arhizodont arvicoline rodent is described from early Pleistocene deposits of Barranco de los Conejos and Barranco del Paso in the Guadix–Baza Basin of southern Spain. The molars of Orcemys appear to represent a paedomorphic origination from a large rhizodont Mimomys. A few dental characters of Orcemys are superficially similar to those of the lagurines, but the presence of sparse cementum in reentrant folds and a Mimomys-kante formed opposite T5 on the first lower molar clearly identify Orcemys as an arvicoline. The character mosaic of Orcemys is unique among large early Pleistocene voles and the dentition of a potential ancestor probably resembled that of Mimomys medasensis with a tendency towards simplification. With Tibericola vandermeuleni and Mimomys oswaldoreigi, Orcemys represents one of the earliest experiments with arhizodonty among European voles. Including Mimomys medasensis at Barranco del Paso, this set of arvicolids redefines a previously recognized early Pleistocene MmQ1 biozone in Spain.
Un nouveau rongeur arvicoliné arhizodonte est décrit dans les dépôts du Pléistocène inférieur de Barranco de los Conejos et de Barranco del Paso dans le bassin de Cadix–Baza, en Espagne méridionale. Les molaires d’Orcemys semblent représenter une origine pédomorphique à partir d’un grand rhizodonte, Mimomys. Quelques caractéristiques dentaires d’Orcemys sont superficiellement similaires à ceux des lagurinés, mais la présence de cément épars dans les plis rentrants et un T5 formé à l’opposé de Mimomys-kante sur la première molaire inférieure identifient Orcemys comme un arvicoliné. La mosaïque de caractères d’Orcemys est unique parmi les grands campagnols du Pléistocène inférieur, et la dentition d’un potentiel ancêtre ressemble probablement à celle de Mimomys medasensis, avec une tendance à la simplification. Avec Tibericola vandermeuleni et Mimomys oswaldoreigi, Orcemys représente les essais les plus précoces d’arhizodontie parmi les campagnols européens. Si l’on inclut Mimomys medasensis dans Baqrranco del Paso, cet ensemble d’arvicolidés redéfinit une biozone MnQ1 reconnue antérieurement au Pléistocène inférieur en Espagne.
Spain, Pleistocene, Arvicolid, Guadix–Baza Basin, BiostratigraphyEspagne, Pléistocène, Arvivolidé, Bassin de Cadix–Baza, BiostratigraphiepresentedPresented by Lars vanden Hoek OstendeIntroduction
Although the first arhizodont arvicolid rodents are known from the Pliocene (the Lemminae and Pliophenacomyinae [Zakrzewski, 1984], [Fejfar and Repenning, 1998]), during the early Pleistocene about 2.0 Ma (million years ago) arvicoline rodents with rooted molars began experimenting with arhizodonty. This group included voles of the nascent tribes Arvicolini and Lagurini originating from a vast radiation of mimomyine voles, predominantly in the Old World, and the Dicrostonychini, probably originating in the New World.
Among the earliest well-dated representatives of this radiation is Microtus (Allophaiomys) from the Short Haul locality of Kansas, USA, currently morphologically inseparable from M. pliocaenicus from the Betfia 2 locality of Romania (Hir, 1998, Kormos, 1933 and Martin, 2008). Short Haul is bounded below by the Huckleberry Ridge ash dated at 2.11 Ma and above by the base of the Olduvai subchron (Martin et al., 2008). The importance of the Short Haul record is that it documents an ancient age for the origination of Microtus and also suggests that early Pleistocene European Microtus are the result of a later dispersal, probably originating in Asia. Other arhizodont arvicoline genera appearing during the early Pleistocene include the Old World Arvicola, Chionomys, Tibericola, Stenocranius and Victoriamys (Agustí et al., 2013, Cuenca-Bescós et al., 2016 and Martin, 2012). Early Pleistocene arhizodont voles also originating as end members of endemic mimomyine stems in East Asia include Huanonomys and Heteromimomys (Zhang et al., 2010 and Zheng, 1992). Another evident descendant of the Old World mimomyine radiation that reached North America (Tesakov and Kolfschoten, 2011) is a relative of the North American sagebrush vole, Lemmsicus curtatus, recovered from early Pleistocene deposits (probably between 0.78–1.0 Ma) in Porcupine Cave, Wyoming (Bell and Barnosky, 2000). According to Koenigswald and Tesakov (1997), rootless lagurines, represented by the transition from rhizodont Borsodia to arhizodont Prolagurus (= Lagurodon), occurred in eastern Europe at a point subsequent to the arrival of Allophaiomys close to the Olduvai subchron (perhaps between 1.90–1.75 Ma). Another lineage of lagurines, Kalymnomys, endemic to the Aegean-Anatolian region of southeastern Europe and western Asia, developed arhizodont molars prior to the dispersal of Allophaiomys, possibly between 2.1–1.9 Ma (van den Hoek Ostende et al., 2015).
One of the regions in Eurasia with a very dense Late Cenozoic fossil record is the Iberian Peninsula. This region documents the evolution of rhizodont mimomyine vole assemblages of the Villanyian into arhizodont arvicoline voles of the Biharian with several lineages representing a combination of autochthonous evolution and dispersal from the Eurasian mainland. In 2005, J. Gibert (Institut. Paleontologia Crusafont) provided R. Martin with arvicolid fossils recovered from Barranco (B.) del Paso in the Guadix–Baza Basin. Among the material were a number of molars from a large, arhizodont species with a high dentine tract at the position of the Mimomys-kante (ridge) (Fig. 1). Thinking that the taxon might be a large Iberian relative of Borsodia (Tesakov, 1993), Martin sent illustrations to A. Tesakov, at which point Tesakov suggested the taxon was an arvicoline and likely new. Unknown to Martin and Tesakov, J. Agustí (IPHES) had found a few molars of the same taxon at B. de los Conejos. Agustí et al. (2013) published an illustration of a first lower molar (m1) of the new taxon from B. de los Conejos and tentatively concluded it represented rootless Mimomys medasensis. At a recent workshop on arvicolid rodents held in Berlin, Germany as part of the 2014 annual meeting of the Society of Vertebrate Paleontology, Tesakov and Martin examined the B. del Paso arvicolid material and concluded that enough specimens were available to define and justify a new taxon separate from M. medasensis. They invited Agustí to join them in the description of this taxon, resulting in the contents that follow.
Dental terminology and measurements
Arvicolid molar occlusal morphology and terminology of the crown-root junction, the linea sinuosa (Fig. 2), follow Meulen (1973) and Rabeder (1981). Lower molars are designated by lower case, uppers by upper case letters; acc = anteroconid complex, acd = anteroconid of first lower molar (m1). Anterior and posterior enamel edges of triangles, as seen in occlusal morphology under the dissecting microscope, may display distinct differences in thickness (be differentiated). The term negative enamel differentiation applies if the posterior (trailing) edges in the lowers are thicker than the anterior (leading) edges (opposite in the uppers – anterior edges thicker). Most Mimomys dentitions display negative differentiation. Positive enamel differentiation describes the condition in which the posterior edges are thinner than the anterior edges in the lowers (opposite in the uppers). Most Microtus species have positive differentiation. A few extinct and extant arhizodont voles display the undifferentiated condition, in which anterior and posterior edges are of equal thickness. As shown by Martin et al. (2006), molars that appear undifferentiated under the light or dissecting microscope may actually be slightly differentiated if edges are measured more accurately under the electron microscope. Rhizodont molars possess roots; arhizodont molars are rootless and evergrowing. Hypsodont = high-crowned, hypselodont = high-crowned and rootless. The m1 in some archaic arvicoline genera, including Mimomys, is characterized by the presence of a unique structure named the Mimomys-kante. This is an enamel projection from the anterior border of T4 that breaks the standard third buccal (labial) reentrant fold (BRA3) of arvicolid m1s into two new folds. The fold posterior to the Mimomys-kante is referred to as the prism fold (Fig. 1).
All measurements are greatest measurements on the occlusal surface. The BTQ, or Basic Triangle Quotient, of Tesakov (1998) was used to quantify enamel differentiation of the m1 as follows:BTQm1=100×SDQ1+SDQ2+SDQ33,
\[
\text{BTQ}\text{\hspace{0.28em}}\text{m1}=100\times \frac{\left(\text{SDQ1+SDQ2+SDQ3}\right)}{3}\text{,}
\]where SDQn = thickness of anterior (leading) enamel edge/thickness of posterior (trailing) edges in the first three primary triangles (T1–T3). Differentiation categories are recognized as BTQ > 100 = positive differentiation, BTQ = 100 = undifferentiated, BTQ < 100 = negative differentiation.
The microhistological enamel banding pattern of the occlusal molar surface as seen under the scanning electron microscope (SEM) is known as the schmelzmuster (Koenigswald, 1980). L = lamellar enamel, T = tangential enamel, R = radial enamel. Incipient tangential enamel (IT) is intermediate between radial and well-developed tangential enamel, in which enamel prisms are bent at a 45o angle and the edges are not flat and feathered. A L–R pattern on the anterior (leading) edges of a triangle on the lower molars implies that the inner band was composed of lamellar enamel and the outer of radial enamel. Further definition of these terms can be found in Martin et al., 2006 and Martin et al., 2003. Schmelzmuster photos were taken with an FEI Quanta 600 ESEM.
A phylogenetic analysis was done with MacClade 4.06 (Maddison and Maddison, 2001) including Orcemys and select arvicolids. Characters and a data matrix are found in Appendix I. Promimomys insuliferus was chosen as the outgroup. The comparison was made only with large Mimomys species (mean m1 length ≥ 3.30 mm), as it was assumed that the arhizodont dentition of O. giberti originated as a paedomorphic population from a large rhizodont ancestor.
OM = Orce Museum (Centro Interpretación Primeros Probladores Jose Gibert), BP = Barranco del Paso, IPHES = Catalan Institute of Human Palaeoecology and Social Evolution.
Locality and horizon–B. de los Conejos and B. del Paso, Guadix–Baza Basin, Granada, Spain; early Pleistocene, above Olduvai subchron, perhaps 1.5–1.7 Ma.
Etymology–Orcemys, after the area in the Guadix–Baza Basin that has produced a series of important paleontological localities; giberti, in honor of the late Josep Gibert y Clols, for his pioneering work with Pleistocene mammals in the Guadix–Baza Basin.
Diagnosis of genus and species–Size large (m1 > 3.30 mm); molars rootless and hypsodont; triangles with acute rather than rounded or bulbous tips, widest at bases; enamel negatively differentiated or undifferentiated; cement absent to minimal in reentrant folds; lingual reentrant folds on m1 horizontal to slightly provergent; schmelzmuster L-R on leading and R-IT on trailing edges (Fig. 4); Mimomys-kante narrow, somewhat elongated and located opposite base of T5; high dentine tract (the mimosinuid of Rabeder, 1981) on m1 at Mimomys-kante breaking through enamel on occlusal surface with minimal wear; BRA3 and LRA4 on m1 shallow, resulting in simple acd without pronounced lingual extension; T1-T2 on m1 widely confluent; T1-2 and T3-4 widely confluent on m2; T3-4 widely confluent on m3; T4 reduced on m3; enamel atolls absent from m1 and M3; M3 simple, with 2 labial and 2 lingual reentrant folds; anterior loop on M3 lingually narrowed and broadly confluent with T2; T3 widely confluent with posterior cap on M3; T4 on M3 minimally developed.
Differential diagnosis of the genus. Differs from Mimomys in having rootless molars, from genera of the Microtini in having sparse cement, nearly straight walls of occlusal triangles and simple M3.
Description of dentition – With the exception of the holotype m1 and paratype M3, the following description pertains primarily to the specimens from B. del Paso.
m1: The m1 is composed of three triangles and the anteroconid complex. A slim and relatively elongate Mimomys-kante is developed from the anterior enamel border of T4. A high mimosinuid breaks through the occlusal surface at the Mimomys-kante in the holotype from B. de los Conejos and two m1s from B. del Paso in which this area is preserved. Another, shallower fold forms the anterior border of the Mimomys-kante, leading to a small, simple, circular to oblong anterior cap. The enamel ranges from negatively differentiated to undifferentiated. An enamel atoll is absent in three adult m1s. In the holotype m1 and referred specimen OM–BP0101, thin dentine tracts connect the posterior loop with T1, T2-T3, and T3-acd. A relatively wide dentine isthmus connects T1–T2 in both specimens. In the m1 OM-BP0103, dentine tracts connect both T1–T2 and T2–T3, creating a relatively wide dentine field between these triangles. Differences in BTQ between the holotype and OM-BP0101 are well within the boundaries of individual variation for BTQ values (Martin et al., 2006).
m2: T1–T4 well developed. T1–T2 widely confluent (Fig. 4).
m3: Similar form to m2, except T4 is much reduced.
M1–M2: only one partial upper molar, probably a piece of M1, is available from B. del Paso. T3 is closed from T4, but nothing distinctive can be seen on this specimen.
M3: The M3 is simple, with an anterior loop, two triangles (T2 and T3) and a small, posteriorly extended posterior cap. BRA3 is negligibly developed and LRA3 is shallow. The anterior cap is widely confluent with T2 and T3 is widely confluent with the posterior cap. Enamel atolls are absent. The anterior loop is asymmetrical and can be considerably lingually narrowed. In general form, it somewhat resembles the M3 of the lagurines Borsodia and Lagurodon.
Cementum is mostly absent from the reentrant folds between triangles, but a slight bit of cementum can occasionally be seen adhering to the walls of reentrant folds. This feature discriminates O. giberti from contemporaneous Mimomys medasensis and Tibericola vandermeuleni, in which cementum is well-developed, and also from the lagurines, in which cementum is absent.
DiscussionPhylogenetic Relationships
The combination of characters expressed by Orcemys as shown by the cladogram in Fig. 5 is unique among Eurasian arvicolids. The unusual acc form of the m1, with a narrow, elongate Mimomys-kante associated with a high mimosinuid, is found in Mimomys medasensis, M. malezi, Heteromimomys zhengi, Borsodia arankoides and Lagurodon arankae in Eurasia and Mimomys (Cromeromys) species from Eurasia and North America, but only L. arankae is fully arhizodont. The M3 morphology of O. giberti, with an asymmetrical anterior loop and narrow, extended posterior cap, is decidedly lagurine in shape, as is the simple anteroconid shape of m1 anterior to the Mimomys-kante (Fig. 6). However, the presence of cementum in the reentrant folds and the position of the Mimomys-kante opposite T5 on m1 clearly demonstrate derivation from an ancestral arvicoline. Also, by the time advanced, occasionally arhizodont, Lagurodon appear in eastern Europe enamel differentiation is positive, unlike the condition in Orcemys in which differentiation is primarily negative to undifferentiated. Dental similarities of O. giberti molars to those of the lagurines are therefore convergent.
Agustí et al. (2013) suggested that the B. de los Conejos O. giberti represented rootless Mimomys medasensis, a species described initially by Michaux (1971) from Islas Medes off the northern coast of Spain. However, as shown by Michaux (1971), the juvenile morphology of M. medasensis m1s from the type locality differs from the morphology of O. giberti. Juvenile m1s of M. medasensis usually display an enamel atoll in the acd. Additionally, as in all other large Mimomys but not in Orcemys, juvenile M. medasensis display a bulbous lingual projection from the anterior end of the acd due to relatively deep penetration of LRA4 (Fig. 6). LRA4 shallows out in M. medasensis with later wear. BRA3 also tends to be relatively deep in juvenile M. medasensis m1s. In contrast, the m1 of O. giberti never displays deep LRA4 or BRA3, resulting in a simple and relatively narrow acc form at all wear stages. The M3 of M. medasensis is also typical for Mimomys, with a wide posterior cap enclosing an enamel atoll, whereas the M3 of O. giberti is more lagurine in its morphology. Thirty-six molars of M. medasensis in all wear stages were identified with O. giberti from B. del Paso. Root formation was observed in all specimens, including the least worn specimens with crown height comparable to molars of O. giberti. So, O. giberti molars are not juvenile M. medasensis molars. However, a relationship with M. medasensis remains possible.
A number of the dental features of O. giberti are those that one would expect if O. giberti molars were paedomorphic forms inherited from an ancestral large rhizodont Mimomys, including absence of roots, minimal cementum in the reentrant folds and a more angular (prismatic) appearance of individual triangles. Mimomys medasensis and the earlier M. ischus/gusii complex occasionally display the high mimosinuid of O. giberti (Agustí et al., 2013 and Esteban and Martínez-Salanova, 1987), but not the simple morphology of m1 and M3. Nevertheless, the ancestor of O. giberti must have possessed a dentition resembling that of M. medasensis in which juvenile m1 and M3 morphology tended towards simplification, and it is conceivable, perhaps even likely, that O. giberti evolved from a currently unrecovered population of M. medasensis or an Iberian Mimomys ancestral to both. In his original diagnosis of M. medasensis, Michaux (1971) noted that the anterior cap of m1 was relatively narrow and the atoll on m1 was reduced in size relative to other Mimomys species.
Biochronology
In their recent description of rodent biostratigraphy in the Guadix–Baza basin, Agustí et al. (2015) listed Mimomys medasensis as an associate of Mimomys (= Kislangia) gusii from their Kislangia gusii biozone, representing the MN (Mammal Neogene) 17 zone. Mimomys medasensis is present at B. del Paso but absent from B. de los Conejos. This difference in rodent faunal composition could therefore represent a difference in age between the latter sites. While there may be a temporal difference between the B. del Paso and B. de los Conejos localities, we suspect the difference is slight, and neither is likely to be as old as the sites of Galera 2 and Zújar 14 from the K. gusii biozone. The combination of O. giberti, (arhizodont) Tibericola vandermeuleni and Mimomys oswaldoreigi defines the Mimomys oswaldoreigi biozone of Agustí et al. (2015) and Arvicolid Zone 1 of Martin, 2012 and Martin, 2016. In eastern Europe, this interval correlates with the early Tamanian (= Odessian) faunal horizon of the eastern European “Eopleistocene” (Rekovets and Nadachowski, 1995) and regional biochrons MQR 11-10, equivalent to the early Biharian of western Europe (Tesakov, 2004). The early Tamanian is characterized by the earliest arhizodont Microtus, M. deucalion. Known from a number of localities in the Black Sea region of the Ukraine and Russia, M. deucalion apparently ranges from just beneath the Olduvai subchron to about 1.6 Ma (Tesakov, 2004). No arhizodont arvicolids have been reported from European sites allocated to MN 17, the latter which is considered to be > 2.0 Ma in age (Fejfar et al., 1998). Although Mimomys medasensis was tentatively recorded from MN 17 (Opdyke et al., 1997), this material has not been studied in detail and it is unclear if the second large Mimomys from Galera 2 and Zújar 14 (besides M. gusii) is the same species that we report here as M. medasensis from B. del Paso. Scott et al. (2007) also reported that B. del Paso was deposited in sediments above the Olduvai subchron. The similarity of rodents, especially the arhizodont O. giberti and T. vandermeuleni, between B. del Paso and B. de los Conejos suggests that B. de los Conejos was also deposited after the Olduvai subchron. Agustí et al., 2013 and Agustí et al., 2015 provided a slightly older range for the Mimomys oswaldoreigi biozone, from about 2.0–1.6 Ma, but given all the available evidence we propose that B. del Paso and B. de los Conejos were deposited after Fuentenueva-1 during the period 1.5–1.7 Ma.
Acknowledgments
Fossil collection in the Meade Basin of Kansas was supported by the National Geographic Societyhttp://dx.doi.org/10.13039/100006363 (5963-97, 6547-99) and the National Science Foundationhttp://dx.doi.org/10.13039/100000001 (EAR 0207582, EAR 1338262). Collections at B. de los Conejos by J. Agustí were part of projects CGL 2016-8000-P and SGR2014-901 (Gentcat) and those from B. del Paso by J. Gibert were funded by the Early Man in Spain project (Earthwatch Institutehttp://dx.doi.org/10.13039/100001089). The work of A. Tesakov was partly supported by the Russian Foundation for Basic Research, Project 15-05-03958.
Characters and matrix used for phylogenetic analysis.
Form m1 (unordered): 1 = atoll present, 3 Ts, T4-5 undeveloped on acd; 2 = atoll present, 3 Ts + T4-5 incipient on acd, BRA3 & LRA4 relatively deep; 3 = atoll present or absent, anterior end acd narrow and simple; 4 = atoll absent, Mimomys-kante absent.
Form M3 (ordered): 1 = ant loop not distinctly assymetrical, post loop relatively broad and short; 2 = ant loop asymmetrical, labially extended and narrow; post loop narrow and extended.
Mimosinuid (numbers refer to relative development from base of crown-root junction)(ordered): 1 = minimal development, 2 and 3 = more developed, 4 = breaks through occlusal surface with minimal wear.
Hyposinuid (numbers refer to relative development from base of crown-root junction)(ordered): 1 = minimal development, 2 and 3 = more developed, 4 = breaks through occlusal surface with minimal wear.
AgustíJ.BlainH.-A.FurioM.De MarfaR.Martínez-NavarroB.OmsO.Early Pleistocene environments and vertebrate dispersals in western Europe: the case of Barranco de los ConejosQuat. Int.295201359–68AgustíJ.GalobartA.Martin-SuárezE.M.Kislangia gusii sp. nov., a new arvicolid (Rodentia) from the late Pliocene of SpainScripta Geol.1031993119–134AgustíJ.Lozano-FernándezI.OmsO.PiñeroP.BlainH.-A.López-GarcíaJ.M.Martínez-NavarroB.Early to middle Pleistocene rodent biostratigraphy of the Guadix–Baza Basin (SE Spain)Quat. Int.3892015139–147BellC.A.BarnoskyA.D.The microtine rodents from the Pit locality in Porcupine Cave, Park County, ColoradoAnn. Carnegie Mus.69200093–134Cuenca-BescósG.BlainH.-A.RofesJ.López-GarcíaJ.M.Lozano-FernándezI.GalánJ.Núñez-LahuertaC.Updated Atapuerca biostratigraphy: small mammal distribution and its implications for the biochronology of the Quaternary in SpainC. R. Palevol.152016615–619EstebanF.J.Martínez-SalanovaJ.Mimomys ischus n. sp. y M. realensis n. sp.: dos nuevos arvicolidos (Rodentia, Mammalia) del Plioceno de la Cuenca del Júcar. (Albacete)Estud. Geol.431987299–308FejfarO.RepenningC.A.The ancestors of the lemmings (Lemmini, Arvicolinae, Cricetidae, Rodentia) in the early Pliocene of Wölfersheim near Frankfurt am Main, Germany, Senck. Lethaea771998161–193FejfarO.HeinrichW.D.LindsayE.H.Van KolfschotenT.GibbardP.L.The dawn of the Quaternary: proceeding of the SEQS EuroMam symposium1998Nederlands Institute of Applied Geoscience TNO, National Geological SurveyHaarlem533–553HirJ.The Allophaiomys type-material in the Hungarian collectionsPaludicola2199828–36van den Hoek OstendeL.W.DiepeveenF.TesakovA.SaracG.MayhewD.AlçiçekM.C.On the brink: micromammals from the latest Villanyian from Biçakçi 31 (Anatolia)Geol. J.502015230–245KoenigswaldW.von.Schmelzstruktur und morphologie in dem molaren der Arvicolidae (Rodentia). Abh. SenckNatur. Gesel.53919801–129KoenigswaldW.vonTesakovA.The evolution of the schmelzmuster in Lagurini (Arvicolinae, Rodentia)Palaeontographica245199745–61KormosT.Neue Wühlmäuse aus dem Oberpliozän von Püspökfürdö. Neues Jahrb. MinerGeol. Paläontol.691933323–346MaddisonD.R.MaddisonW.P.MacClade 4.03: analysis of phylogeny and character evolution2001SinauerSunderland, MassachusettsMartinR.A.ArvicolidaeJanisC.M.GunnellG.G.JacobsL.Evolution of Tertiary Mammals of North AmericaII2008Cambridge University PressNew York480–497MartinR.A.Victoriamys, a new generic name for Chaline's vole from the Baza Basin of southern Spain. Pleistocene of western EuropeGeobios452012445–450MartinR.A.Taxonomic issues of some early Pleistocene arhizodont volesRibotT.F.Homenaje al Dr. José Gibert Clols. Una vida dedicada a la ciencia y al conocimiento de los primeros europeos2016Publicaciones Disputación de Granada273–280MartinR.A.CrockettC.O.MarcoliniF.Variation of the schmelzmuster and other enamel characters in molars of the primitive Pliocene vole. Ogmodontomys from KansasJ. Mam. Evol.132006223–241MartinR.A.Duobinis-GrayL.CrockettC.P.A new species of early Pleistocene Synaptomys and its relevance to southern bog lemming originsJ. Vert. Paleontol.232003917–936MartinR.A.Peláez-CampomanesP.HoneyJ.J.FoxD.L.ZalrzewskiR.J.AlbrightL.B.LindsayE.H.OpdykeN.D.GoodwinH.T.Rodent community change at the Pliocene-Pleistocene transition in southwestern Kansas and identification of the Microtus immigration event on the Central Great PlainsPalaeogeogr. Palaeoclimatol. Palaeoecol.2672008196–207MeulenA.J.van.der.Middle Pleistocene smaller mammals from the Monte Peglia, (Orvieto, Italy) with special reference to the phylogeny of Microtus (Arvicolidae, Rodentia)Quaternaria1719731–144MichauxJ.Arvicolinae (Rodentia) du Pliocène terminal et du Quaternaire ancient de France et d’EspagnePalaeovertebrata41971137–214Minwer-BarakatR.Martín-SuárezE.FreudenthalM.Arvicolidae (Rodentia) from the Pliocene of Tollo de Chiclana (Granada, SE Spain)Geobios372008619–629OpdykeN.MeinP.LindsayE.H.Perez-GonzalezA.MoissenetE.NortonV.I.Continental deposits, magnetostatigraphy and vertebrate paleontology, late Neogene of eastern SpainPalaeogeogr. Palaeoclimatol. Palaeoecol.1331997129–148RabederG.Die arvicoliden (Rodentia, Mammalia) aus dem Pliozän und dem älteren Pleistozän von Niederösterreich, Beitr. Paläontol81981Österreich. Instit. Paläontol. Univ. Wien1–373RekovetsL.NadachowskiA.Pleistocene voles of the UkrainePaleontol. Evol.28–291995145–245ScottG.R.GibertL.GibertJ.Magnetostrtigraphy for the Orce region (Bas=za Basin), SE Spain: new chronologies for Early Pleistocene faunas and hominid occupation sitesQuat. Sci. Rev.262007415–4345TesakovA.Evolution of Borsodia (Arvicolidae, Mammalia) in the Villanyian and in the early BiharianQuat. Int.19199341–45TesakovA.Early stage of Allophaiomys evolution in eastern EuropePaludicola2199898–105TesakovA.Biostratigraphy of middle Pliocene-Eopleistocene of eastern EuropeTrans. Geol. Inst. Moscow55420041–446TesakovA.KolfschotenT.van.The Early Pleistocene Mimomys hordijki (Arvicolinae, Rodentia) from Europe and the origin of modern Nearctic sagebrush voles (Lemmiscus)Palaeontol. Electronica1420111–11ZakrzewskiR.J.New arvicolines (Mammalia: Rodetia) from the Blancan of Kansas and NebraskaGenowaysH.H.DawsonM.R.Contributions in Quaternary vertebrate paleontology: a volume in memorial to John E. Guilday, Special Publication 81984Carnegie Museum of Natural HistoryPittsburgh200–217ZhangY.JinCh.KawamuraY.A distinct large vole lineage from the Late Pliocene–Early Pleistocene of ChinaGeobios432010479–490ZhengS.Huananomys, a new genus of Arvicolidae (Rodentia) from the Hexian hominid site, Anhui. VertbrPalAsiatica301992146–161
Generalized Mimomys left m1 with a high mimosinuid on the Mimomys-kante (mK) breaking through the occlusal surface. Pf: prism fold; PL: posterior loop; T: triangle; ACC: anteroconid complex.
M1 gauche de Mimomys avec une mimosinuide élevée sur la brisure de Mymomys-kante au travers de la surface occlusale. Pf : pli de prisme ; PL : boucle postérieure ; T : triangle ; ACC : complexe antéroconide.
A, Left lower and B, left upper, arvicolid molars with labeled topography. ACC: anteroconid complex; TTC: talonid-trigonid complex; AC: anteroconid; PL: posterior loop; AL: anterior loop; PC: posterior cap; T: triangle; BSA: buccal salient angle; LSA: lingual salient angle. C. Sinuids (dentine tracts; or “enamel-free areas”) on labial side of m1. Asd: anterosinuid; Misd: mimosinuid; Pmsd: prismosinuid; Prsd: protosinuid; Hsd: hyposinuid.
A, molaires d’arvicolidés inférieures gauches, B, supérieures gauches, avec topographie marquée. ACC : complexe antéroconide ; TTC : complexe talonide-trigonide ; AC : antéroconide ; PL : boucle postérieure ; AL : boucle antérieure ; PC : couronne postérieure ; T : triangle ; BSA : angle buccal saillant ; LSA : angle lingual saillant. C. Sinuides (zones de dentine ou « zones ne comportant pas d’émail » sur le côté labial de m1. Asd : antérosinuide ; Misd : mimosinuide ; Pmsd : prismosinuide ; Hsd : hyposinuide.
Orcemys giberti from the Guadix–Baza basin, Spain. Occlusal (A) and labial (B) views of holotype Lm1, IPHES BC-030 and occlusal view (C) of paratype LM3, IPHES BC-036, B. de los Conejos. Occlusal view (D) of Lm1, OM-BP 0101 and RM3, OM-BP 0111, B. del Paso. Lines: 1 mm, top for A, C, D, E; bottom for B.
Orcemys giberti du bassin de Cadix–Baza, Espagne. Vues occlusale (A) et labiale (B) de l’holotype Lm1, IPHES BC-030 et vue occlusale du paratype LM3, IPHES BC-036, bassin de los Conejos. Vue occlusale (D) de Lm1, OM-BP 0101 et RM3, OM-BP 0111, B. del Paso. Lignes : 1 mm, sommet pour A, C, D, E, base pour B.
Scanning electron microscope image of Rm2 (61 × ), OM-BP 0106 of O. giberti from B. del Paso, Baza Basin, Spain. Exploded image (492 × ) is of tip of T2 showing LR-RIT schmelzmuster (enamel banding pattern). L: lamellar; R: radial; IT: incipient tangential.
Image au microscope électronique à balayage de Rm2 (61 × ), OM-BP 0106 de O. giberti de B. del Paso, bassin de Baza, Espagne. Image en éclaté (492 × ) de l’extrémité de T2 montrant LR-RIT schmelzmuster (arrangement rubané de l’émail). L : lamellaire ; R : radial ; IT ; tangentiel naissant.
Cladogram resolving relationships of O. giberti based on comparisons in Appendix I.
Cladogramme résolvant les relations de O. giberti, basé sur comparaisons (Appendice I).
Comparison of m1 and M3 morphologies between O. giberti and select species of Mimomys and Borsodia. A-C, Q: Mimomys medasensis, Medes Islands, Spain (from Michaux, 1971); D–F (E is juvenile): M. ischus, Almenara (Casablanca) 1, Spain (from Agustí et al., 1993); G–H: O. giberti, B. de los Conejos, Spain; I (reversed), M. hassiacus from Tollo de Chiclana 1B (from Minwer-Barakat et al., 2008); J, R (reversed): M. cappetai, Balaruc II, France (from Michaux, 1971); K–P (O–P reversed): Borsodia arankoides, Kryzhanovska 4, Ukraine (from Tesakov, 1998). Arrows identify position of Mimomys-kante relative to base of T5. Figures not to scale.
Comparaison des morphologies de m1 et M3 entre O. giberti et des espèces sélectionnées de Mimomys et Borsodia. A-C, Q : Mimomys medasensis, îles Medes, Espagne (selon Michaux, 1971) ; D–F (E est juvénile) ; M. ischus, Almenara (Casablanca) 1 (selon Agustí et al., 1993) ; G-H : O. giberti los Conejos, Espagne ; I (retourné), M. hassiacus de Tollo de Chiclana 1B (selon Minwer-Barakat et al., 2008) ; J.R. (retourné), M. cappetai, Balaruc II, France (selon Michaux, 1971) ; K–P (O–P (retourné), Borsodia arankoides, Kryshanovska 4, Ukraine (from Tesakov, 1998). Les flèches identifient la position de Mimomys-kante relative à la base de T5. Les figures ne sont pas à l’échelle.